This paper describes an interferometer system for testing aspheric surfaces
with computer-generated holograms (CGHs). A CGH written by electron-beams
achieves the precise testing of a wide range of aspheric surfaces. A new
algorithm removes the error caused by misalignment of a CGH and a testing
surface. This system can test aspheric surfaces with accuracy 2/10 (P-V value)
and repeatability /5OO (RMS value).